Pancreas is an organ of about 15 cm in length which is located at the back of stomach. The major pancreatic diseases are pancreatic cancer and pancreatitis. Pancreatic cancer is particularly known as one of cancers with increased mortality rate among Japanese in recent years. Causes of pancreatic cancer have not been completely identified, and excessive consumption of animal fat, animal protein, alcohol, etc. due to Westernized dietary habits, smoking and so on are considered to be risk factors. In addition, people having a history of chronic pancreatitis, pancreatolithiasis, diabetes, or acute pancreatitis are also considered to be in high-risk groups. Pancreatic cancer is initiated in cells having an exocrine function, in particular, in cells of the pancreatic duct where pancreatic juice flows, and this type accounts for more than 90% of pancreatic cancers. Early detection of pancreatic cancer is critically important, because it is highly malignant and metastasized to other organs (in particular, to the liver, etc.) at an early stage. The pancreas, however, is surrounded by many organs such as stomach, duodenum, spleen, small intestine, large intestine, liver, and gallbladder, which makes it very difficult to detect the cancer at an early stage. This often results in a distant metastasis and a pancreatic cancer discovered in an advanced stage, well past the treatable and resectable phase.
Examples of serum tumor markers that have already been developed for diagnosing pancreatic cancer include CA19-9 (Non-patent Document 1), Dupan-2 (Non-patent Document 2), CA-50 (Non-patent Document 3), Span-1 (Non-patent Document 4), etc. These markers, however, give positive results even in the cases of pancreatic and liver benign disorders such as chronic pancreatitis, chronic hepatitis, and liver cirrhosis, which poses a problem of specificity. In addition, these markers sometimes give negative results for specific pancreatic cancers, and therefore inadequate as tumor markers for specifically and reliably detecting pancreatic cancers. It has therefore been considered difficult to detect/confirm the presence of a wide range of pancreatic cancers early and reliably by conventional methods.
Further, some patent publications disclose a method for detecting and diagnosing pancreatic cancer using as a marker a gene specifically expressed on tumor cells. To date, PANCIA and PANCIB (Patent Document 1) and KCCR13L (Patent Document 2) have been disclosed as pancreatic cancer marker genes. Furthermore, since a DNA amplification or deletion is found in a specific chromosomal site in pancreatic cancer cells, a method is also proposed for diagnosing pancreatic cancer by detecting the amplification or deletion in the chromosomal site which is specific to pancreatic cancers (Patent Document 3).